ladybird/Userland/Libraries/LibC/sys/select.cpp

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <errno.h>
#include <stdio.h>
#include <sys/poll.h>
#include <sys/select.h>
#include <sys/time.h>
#include <syscall.h>

#include <AK/Vector.h>

extern "C" {

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/select.html
int select(int nfds, fd_set* readfds, fd_set* writefds, fd_set* exceptfds, timeval* timeout_tv)
{
    timespec* timeout_ts = nullptr;
    timespec timeout;
    if (timeout_tv) {
        timeout_ts = &timeout;
        TIMEVAL_TO_TIMESPEC(timeout_tv, timeout_ts);
    }
    return pselect(nfds, readfds, writefds, exceptfds, timeout_ts, nullptr);
}

// https://pubs.opengroup.org/onlinepubs/9699919799/functions/pselect.html
int pselect(int nfds, fd_set* readfds, fd_set* writefds, fd_set* exceptfds, timespec const* timeout, sigset_t const* sigmask)
{
    Vector<pollfd, FD_SETSIZE> fds;

    if (nfds < 0 || static_cast<size_t>(nfds) >= fds.capacity())
        return EINVAL;

    for (int fd = 0; fd < nfds; fd++) {
        short events = 0;
        if (readfds && FD_ISSET(fd, readfds))
            events |= POLLIN;
        if (writefds && FD_ISSET(fd, writefds))
            events |= POLLOUT;
        if (exceptfds && FD_ISSET(fd, exceptfds))
            events |= POLLPRI;
        if (!events)
            continue;

        fds.unchecked_append({ fd, events, 0 });
    }

    if (ppoll(fds.data(), fds.size(), timeout, sigmask) < 0)
        return -1;

    if (readfds)
        FD_ZERO(readfds);
    if (writefds)
        FD_ZERO(writefds);
    if (exceptfds)
        FD_ZERO(exceptfds);

    int marked_fd_count = 0;
    for (auto& fd_entry : fds) {
        if (fd_entry.revents == 0)
            continue;
        if (readfds && (fd_entry.revents & POLLIN)) {
            FD_SET(fd_entry.fd, readfds);
            marked_fd_count++;
        }
        if (writefds && (fd_entry.revents & POLLOUT)) {
            FD_SET(fd_entry.fd, writefds);
            marked_fd_count++;
        }
        if (exceptfds && (fd_entry.revents & (POLLPRI | POLLERR | POLLHUP))) {
            FD_SET(fd_entry.fd, exceptfds);
            marked_fd_count++;
        }
    }

    return marked_fd_count;
}
}